Compensating speed governor, especially for hydraulic turbines



T. W. BROWN Dec. 20, 1955 COMPENSATING SPEED GOVERNOR, ESPECIALLY FORHYDRAULIC TURBINE-S Filed May 27, 1950 m (j P. M O

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c 5 a a 2 a 0 w 22 2 2 4 6 2 g 2 1 l i a g a Patented Dec. 20, 1955COMPENSATHNG SPEED GGVERNOR, ESPECIAL- LY FUR HYDRAULIC TURBINES ThomasW. Brown, Ashiand, Mass, assignor to Lombard Governor Corporation,Ashland, Mass, a corporation of Massachusetts Appiication May 27, 1950,Serial No. 164,774 Qlaims. (Cl. 137-34) My present invention relates togoverning, regulating and control systems and apparatus generally, andespecially as related to governing the speed of prime movers, as forexample, hydraulic turbines. More particularly it aims to provideimproved controlling means having secondary compensating or follow-upmeans in association with a primary servo and pilot or other maincontrolling device.

It is the general practice in hydraulic turbine governor design toprovide a primary means acting back from the supply regulating orgate-operating element for modifying the action of the prime mover speedmeasuring device upon the primary pilot or main motor controllingdevice, to prevent overtravel of the gates with consequent instability.It is also not unusual to employ some secondary means to overcomegradually the larger speed changing effect of such primary means, in aneffort to produce approximately iscchronous governing yet withoutobjectionable instability. However, the provision of such secondarycompensating means presents various problems and heretofore has not beenaccomplished with entire satisfaction.

capable of accomplishing substantially isochronous governing withadequate stability, while avoiding difiicult mechanical fits, use ofcritical springs and the like, or the requirement of extended periodsfor adjustment.

The invention will be more fully understood from the followingdescription taken in con'unction with the accompanying drawingsillustrative of one embodiment thereof, in which:

Fig. l is a schematic view of a fluid-pressure operated hydraulicturbine governor novelly incorporating secondary compensator means; and

Fig. 2 is a schematic view of an alternative form for the compensatorthrottle.

In the selected example the novel governor system and compensator meansis illustrated in association with an hydraulic turbine indicatedgenerally at 10, having an l closes the turbine gate to reduce outputspeed; coversely, counter-clockwise turning of shaft 28 will open thegate and increase the speed.

H In the illustrated application of the invention to govern inghydraulic turbines, it will be understood that the final control orregulating element is the gate shaft 28 of the turbine whereby thecontrol agent, in this instance the hydraulic driving energy supplied tothe turbine, is varied by the automatic governor means here concerned f6give to the variable and regulated quantity the desired value, namely, asubstantially constant speed for the turbine out- 2 put regardless ofchanges, and particularly step changes, in the load.

The governor system comprises first a metering and force relayingelement shown as a tachometer of the centrifugal type, of known orpreferred construction, designated generally at 16. It has a spindle 17driven from the turbine pulley 12 as by a belt 13 passing over a guidepulley 14 to a pulley 15. The latter is held from axial movement whilethe spindle 17 is slidably splined or otherwise angularly fixedcoaxially in it, with capacity to shift axially, vertically in thediagram, under output speed change at the turbine.

The centrifugal action of the revolvable masses or flyballs 18a, 18ahung on the spindle 17 and their attendant radial movement is convertedto axial movement of the spindle, downward in the drawing under turbinespeed increase, and vertically upward under speed decrease. A

end of the lever 20 as at 20a. The slidable valving spool element 22a ofthe three-Way pilot valve 22 cooperates with upper and lower ports toclose both in the neutral or equilibrium position, and to open one whileclosing the other in upper and in lower positions, reversely, therebyplacing the opened port in communication with the comcrank arm 27 on thegate shaft 23 and connected to the servo piston 26a as by a rod 26b.Piston movement to the right turns the gate shaft 28 clockwise, in thegate pilot valve 22. It is normally, as during periods 'of no change'inthe turbine load, balanced between the operating fluid pressure from thetank 25 through a branch line 250 to the smaller piston face, and theremaining pressure at the larger piston face, at the left in thediagram, under the closed-off neutral position of the pilot valve 22. 7t

In this neutral position both the pressure tank 25 and movement, porteither the upper or the lower pipe 230 brZS'a throughthe valvetoth'eline 24 to the larger face of the servomotor piston --26a. -In thediagram down movement of the tachometer spindle 17 and of valve spool22a opens thelower valve port and thus through lines "25a Land-24subjects said larger piston "face to the oil pressure from the supplytank, thereby moving the pistonfifia toward'the'right on'thedrawing,'-to close the gate. Conversely, opposite upward movement of thespindle 17' and val-vespool 22a subjects said larger face of' 'the servopiston' 26a-to the lower pressure side of the system, through the line24, the then open upper port of valve 22 an'dthe'upper pipe 23a leadingto the sump '2'3, with resu'ltantpistontravelto the left onthe' drawing,in the gate opening direction.

"'By way-"of summary tothispoinnthe desired constant output speed forthe turbine over a range of loads requires corrective variation of theturbine input energy at' thegate directly with theload 'and'inverselywith the output speed. The described'primary control accordingly Closesthe gate under speed'increase (load decrease) and opensitunder'speedreduction (load increase). With descent ofthe spindle 17under speed increase the servo piston'26a'movesto theright and'turns'thegate shaft'23 clockwise-to close the gate in-the speed decreasingdirection. And with rise of the spindle 17 under speed decrease theservo piston 26a goes to the left and the gate shaft-28 is turnedcounter-clockwise in the gate opening and speed increasing direction.

Topreventovertravel'of the gate and consequent instability in thegoverning action it is common practice to employ aprimarycomp'ensatingmeans or follow-up. Herein such primary compensatingmeansto modify the action oftherelay'governor 16"on the primary controlvalve-orpilot 22 comprises a'verticallink 31connected as zit- 201;totheendof the lever '20 distal 'to' theprimary valve 22. This-link 31isintermediately connected as at 31 a toa secondhorizontal'lever 30. Theright .end of the latter is pivoted as at 3'0bto the upper end of a'followup=link29 the lower end of which is pivoted to a short lever-arm27a angularly fixed with the lever 27 on the gate shaft 28 previouslydescribed. As will be more fully apparent hereinafter, action of thisprimary compensating means 270:, 29, 31, b is to return the primarypilot or control valve 22 to neutral, as illustrated in Fig. l,in-response to regulating movement of the gate shaft 28, and thusreestablish an equilibrium.

'Butwith such primary compensation if alone and unmodified suchequilibrium is restored at a substantially differentturbine speed-thanwas in effect before the load change. Accordingly a secondarycompensating means, which is-itself susceptible of appropriateregulation, is herein novelly provided. The'purpose of'this secondarycompensating means is to overcome the stated turbine speed'ch'ange ordeviation from original speed before the load change, by maintaining animbalance in the governor-until the turbine speed has been returned toapproximately its initial value, thereby producing such isochronousgoverning as is consistent with stability.

As herein illustrated such secondary compensating means of-my presentinvention is'indicated generally at 32, centrally of Fig. 1. Itcomprises a three-way secondary control or pilot valve 33 whichmay'besimilar in type toprimary pilot 22. Operatively associated with itis a secondary se1vomotor'34. The secondary compensating means furthercomprises a lever connection between the secondary pilot andservo,andwith'the follow-up means, together with piping-connections asindicated. The slidable valve 'spool 33a of the secondary pilot 33 isreciprocable by a link 35Iwhich maybe an extension of vertical link 31of the follow-up or primary compensator means. it ispivoted at -31aintermediary of the second horizontal-lever 30 already mentioned.

' The-secondary pilot or-control valve 33 is connected to the sump 23through an upper pipe branch' 23b from the sump line 23a,.and tothepressure tank 25 "through a lower pipe branch 25b from the pressureline 25a. This secondary pilot 33 is adapted to place the lower andlargeface of the piston 34a of the secondary servo 34 alternatively incommunication with the low-pressure or sump side of the system or withthe pressure side. This is accomplished through the pipe connection 36between the common intermediate port of the secondary pilot 33 and saidlower'end of the secondary servo 34. The upper end of the latter, andupper and smaller face of the secondary servo piston 34a have a pipeconnectiorr 25d to the pressure fluid line 2511.

An adjustable flow restrictor or throttle 36a limits the rate of flowthrough the pipe 36 between the secondary servo and its pilot. Underequilibrium conditions piston 34a is balanced in the secondary servo 34by a constant pressure supply from tank 25 through pipe 25d. It iscoupled by its rod 37 to the adjacent end of the second horizontal lever3b as at 30a, opposite to the primary compensator arm connection 3012.It will be seen that the secondary pilot or control valve 33 will beshifted through lever 30 under the combined influence of thezprimarycompensator or follow-up arm 29 and of the secondary servo 34. Thissecondary pilot 33, like main pilot valve 22, will have upper,intermediate, and lower positions in which it supplies variously sump,equilibrium or system, and pressure tank pressures to the larger-areaface of piston 34a of the secondary servomotor 34. The linkage 37, 30,35 in a sense provides a follow-up action between this secondary servo34 and its pilot 33.

Itwill'be obvious that in the operation of the described system andmeans the similar sequence of events will occur in response either to adecrease or to an increase in the turbine load, but with the variousmotions having opposite directions. For purposes of the presentdiscussionit will be assumed that the system has been in operation atthe desired speed under some fixed load in .the turbine, and that thisload decreases suddenly in a step change to another fixed load. Theresultant increase in the regulated quantity or turbine speed willeffect a corresponding increase at the tachometer 16 and the governingapparatus proceeds in effect to cut ofi the necessary amount ofhydraulic energy from the turbine to suit the new load and to operatethe turbine at the same speed as formerly.

Under such load drop and speed increase the attendant radial outwardmovement of the tachometer masses 18a will drop the spindle 17 and thevalve spool 22a of the primary pilot 22. The distal or right end 20b ofhorizontal lever 20 initially remains fixed. Oil from the pressure tank25 is thus admitted to the primary servomotor 26, forcing its piston 26ato the right and rotating gate shaft 28 clockwise to close the turbinegate. Closing of the gate tends to reduce the speed; the speed measuringforce of masses 18a is accordingly reduced and the tachometer spindle 17is permitted to return upward.

Coincident to this, the primary follow-up arm 29 is urged downwardly bythe clockwise rotation of the gate shaft, drawing down with it end 20bof lever 20. The secondary servo piston 34a may be regarded asstationary for the moment. These two results of the gate shaft movementcombine to raise lever end 2011 and primary valve spool 22a to anequilibrium or neutral position, cutting off the oil to servo 26 and sohalting movementof the gate. Assuming suitable adjustments throughout,and supposing the secondary compensating means were inoperative or notpresent, the sequence of events started 'by the initial load change isthus ended. But equilibrium is thus reestablished at a higher turbinespeed than .formerly, due to the fact that a lower position oftachometer spindle '17 will suflice to hold valve 22 closed, in view ofthe lowered position of the end 2012 of lever 20.

Now consider the secondary compensator means including the secondaryservo 34 and its pilot valve 33. With'these present and operative, theabove mentioned otherwise operatable flow restrictor downmovement of thelever end b eifects a like down movement of the secondary valve spool33a, admitting oil from pressure tank to the larger under face of thepiston 34a of the secondary servo 34. This forces said piston 34a andthe adjacent end a of the second horizontal lever 30 upward. Theopposite end 3% of said lever being momentarily fixed, the secondaryvalve spool 33a and the overlying end 20b of the first horizontal lever20 are likewise raised, thus simultaneously tending to return thesecondary valve 33 to its neutral position and the end 20b of lever 20to its original position. This will initially force main valve 22 fromits momentarily established neutral position, in the speed reducingdirection. The result is that the turbine speed is required to returnthrough a rapid series of approximations to its desired initial valuepreliminary tore-establishing equilibrium in the governor system. Itwill be observed that the secondary compensation is mechanicallyopposite to the primary follow-up lever action, thereby tending toprolong the total unbalance until the original speed value is reached.At the same time the secondary compensation aflects the primary pilot inthe same directional sense as did the load change, thereby overcomingthe deviation otherwise resulting as between the regulated speed and theset point or original speed.

The flow of oil from the secondary valve 33 to its associated servoconnection 36, which provides the minimum damping or drag necessary forappropriate governor stability.

same resultant of exact same speed maintenance. In the case of acontinuously changing load the same events will take place, but willoverlap in accordance with the particular form of the load variations,the net eflect of the governing system being to cause the speeddeviations to be minimized.

For certain installations, for example those involving higher turbineloads, having higher inertia and requiring less damping for governorstability, the modified cona secondary compensator corresponding to thatof Fig. 1, other parts of the system being understood as the same. Thesimilar pressure fluid connection between the secondary pilot 33 and theassociated servo 34 is indicated at 36 and the adjusting throttle at36a. In this instance the system further includes a second connectingline 38 between the secondary pilot and servo 33, 34. This may generallyparallel the line 36 and forms a shunt or alternate therefor. In it areincorporated a remote-control on-and-ofl valve 38a herein shown assolenoid operated, and a manually or or throttle 38b. This lattercorresponds in general function to the throttle 36a and has apredeterminedly settable and in assumed higher-load example a smallerthrottling effect than the other throttle 36a. The solenoid of theon-ofl valve 38a is suitably connected for actuation, preferablyautomatically, when the turbine such as 10 is placed under knownheavy-load condition on the power line. The solenoid is therebyenergized to open valve 38a, the eflect of which is to by-pass throttle36a and permit a higher velocity flow through throttle 38b as consistentwith the lesser requirement of damping under the higher inertiaconditions.

It will be understood that for any particular application of the system,the amount of hunting or oscillation which must be removed by the abovementioned throttling for purposes of stability can be predetermined, aswell as whether alternatively selectable speeds of response aredesirable or necessary under given operating loads.

It will be understood that my invention, either as to system, means ormethod, is not limited to the exemplary or described, and I set forthits scope in my following claims.

I claim:

1. In combination with a prime mover having a supply regulating element,a main motor connected to and positioning said element, a pilotcontrolling said motor and having a neutral position when the speed ofthe prime mover is at set point value, a prime mover speed sensingdevice, a first floating lever connected at one end point to said ondarymotor govern said primary pilot directly and also independently one ofthe other.

3. In combination with a prime mover having a supply regulating element,a primary pilot having a neutral position when the speed of the primemover is at set point value, a main motor controlled by said pilot andconnected to and for positioning said supply regulating element, followup means comprising a floating lever connecting said regulating elementto said primary pilot, a prime mover speed sensing device connected tosaid follow up means and to move the primary pilot in one direction fromsaid neutral position upon departure of the prime mover speed from saidset point value, movement of said regnlatingelement efiectingtlirough-said iollow up means returnlmovementnoi said primarytpilottintatdireetionppgositetojsaid one direetiontandtotthet-neutraltposition, and secondary compensatormeansl'includinga-lmotor and. a.

device connected-:toz-saidpilot:andior. moving. the pilot'in' one.tdirection,-. from said neutrabposition (upon. departure ofjthe primernover speed-from saidzsetpoint,value,.fol1ow up: meanseconnenting-rsaid snpplyregulating .elernentgto said primary pilot andw forcoppositreturnamovement of the pilot to the.nentral positiom..a secondary motorand pilot, said secondary pilot connected; to saidnfollow :up meanszandmoving-fromwneutral: position upon said primary-.ipilotz return:movement, said secondary motonconnected to rand for: movingthe primarypilot-z fromthe neutra'l'position and in the same-sense as initiallyby'thespeed sensing device; means 'for selectively varying the rate ofmovement of said secondary "motor comprising parallel fluid. tlinesbetween said. ,rnotQr; and ;1 i.1,0t,v adjustable thl'QifliIlg; elements:in both; said dines, ,andr on-ofi valve means in one said. line.

5 In combinations-with, a. prime. movgarhaving a supplyregulatinglelement; ,a mainnmotor-tconnected to and positioning saidelement; .al pi-lot controlling said motor and having agneutralpositiou; when. the .speedof the prim mover ;is= ,at -se,t -pointvalue,;aspeed-sensing device connected :to. saidzpilotandrvfor movimgthepilot inone direction ,firom said, ,neutral position; upon departure ofthe prime, mover speedlfrom said point value,,fc llctvvv up meansconnectingsaid .supply regulating element to said primary pilQt;andfor.op osite:returnlm v ment-ofthelpilotto h neutral. position, .a.secondaryv .Inotor andv pil t, aid secondary pilotconnected.to,saidf01low.;up,means and moving from. neutral. position.upon .said primary pilot return movement, saidsecondary motorvconnected.to and for moving the pIllIl8Ify..Pi10t from the. neutralposition and in the same senseasinitiallyrbylthespeed sensing device,

parallel .fluid'linesthetweensaid s econdarymotorand pilot,

throttling; elementsin .eachtof said lines. and adapted to fforddifier-ent degrees .of-ithrot lin and rem y c011- trollable valvemeans.nornntlly, .elosingthe lesser-throttled line and.automaticallylqperableto openthe same during predetermined loadconditions.

References Citedfin the file of thispatent UNITED ST TES.- BAEENTS

